E7G Active audio filters:
characteristics; basic circuit design;
preselector applications
E7G01
(B)
What
determines the gain and frequency characteristics of an op-amp RC active
filter?
A. The values of capacitances and resistances
built into the op-amp
B. The values of
capacitances and resistances external to the op-amp
C. The input voltage and frequency of the
op-amp's DC power supply
D. The output voltage and smoothness of the
op-amp's DC power supply
E7G02
(C)
What
causes ringing in a filter?
A. The slew rate of the filter
B. The bandwidth of the filter
C. The filter shape, as
measured in the frequency domain
D. The gain of the filter
E7G03
(D)
What
are the advantages of using an op-amp instead of LC elements in an audio
filter?
A. Op-amps are more rugged and can withstand
more abuse than can LC elements
B. Op-amps are fixed at one frequency
C. Op-amps are available in more varieties than
are LC elements
D. Op-amps exhibit gain
rather than insertion loss
E7G04
(C)
What
type of capacitors should be used in an op-amp RC active filter circuit?
A. Electrolytic
B. Disc ceramic
C. Polystyrene
D. Paper dielectric
E7G05
(A)
How can
unwanted ringing and audio instability be prevented in a multisection op-amp RC
audio filter circuit?
A. Restrict both gain and Q
B. Restrict gain, but increase Q
C. Restrict Q, but increase gain
D. Increase both gain and Q
E7G06
(A)
What
parameter must be selected when designing an audio filter using an op-amp?
A. Bandpass characteristic
B. Desired current gain
C. Temperature coefficient
D. Output-offset overshoot
E7G07
(B)
The
design of a preselector involves a trade-off between bandwidth and what other
factor?
A. The amount of ringing
B. Insertion loss
C. The number of parts
D. The choice of capacitors or inductors
E7G08
(A)
When
designing an op-amp RC active filter for a given frequency range and Q, what
steps are typically followed when selecting the external components?
A. Standard capacitor values
are chosen first, the resistances are calculated, then resistors of the nearest
standard value are used
B. Standard resistor values are chosen first,
the capacitances are calculated, then capacitors of the nearest standard value
are used
C. Standard resistor and capacitor values are used,
the circuit is tested, then additional resistors are added to make any
adjustments
D. Standard resistor and capacitor values are
used, the circuit is tested, then additional capacitors are added to make any
adjustments
E7G09
(C)
When
designing an op-amp RC active filter for a given frequency range and Q, why are
the external capacitance values usually chosen first, then the external
resistance values calculated?
A. An op-amp will perform as an active filter
using only standard external capacitance values
B. The calculations are easier to make with
known capacitance values rather than with known resistance values
C. Capacitors with unusual
capacitance values are not widely available, so standard values are used to
begin the calculations
D. The equations for the calculations can only
be used with known capacitance values
E7G10
(D)
What
are the principal uses of an op-amp RC active filter in amateur circuitry?
A. High-pass filters used to block RFI at the
input to receivers
B. Low-pass filters used between transmitters
and transmission lines
C. Filters used for smoothing power-supply
output
D. Audio filters used for
receivers
E7G11
(D)
Where
should an op-amp RC active audio filter be placed in an amateur receiver?
A. In the IF strip, immediately before the
detector
B. In the audio circuitry immediately before
the speaker or phone jack
C. Between the balanced modulator and frequency
multiplier
D. In the low-level audio
stages